Dyeing processes for wool and preparations therefor



l atented Sept. 9 19 52 2,610,103, DYEING PROCESSES'FOR WOOL PREPARATIONS THEREFOR WilIi Widmer, Bottmingen, Fritz Schuetz, Neue'- welt, near Basel, and Alphonse Heckendorn,

Basel, Switzerland, assignors to Ciba Limited,

Basel, Switzerland, a Swiss firm No Drawing. Application January 20, 1950, Serial No. 139,794. In Switzerland February 11, 1949 20 Claims. (01. 8-26) This invention relates to improvements in dyeing processes and preparations therefor.

Ortho:ortho'-dihydroxymonoazo dyestuffs are known which are of relatively good solubility in a neutral to alkaline medium but are of insufficient solubility in an acid medium. Accordingly these dyestuffs can as a rule not be dyed in a useful process from an acid bath because for the most part they are precipitated by the acid in relatively coarse form and thus even if they still take on the fiber from the suspension, they give non-uniform dyeings and as a rule dyeings of poor fastness properties, for example fastness to rubbing. Moreover undesired deposits frequently occur in the dyebath and espe cially on the wallsof the dye vat. However many dyestuffs of. this type, when they are not dyed from acid bathsbut for examplelaccording to the known single bath chroming process, give very valuabladyeings which are often distinguished by quite particularly good fastness properties. The fact that such valuable products cannot be utilised in acommercially applicable manner for dyeing fireman acid bath, for example, for dyeing by theknown after-chroming process, constitutes aconsidera'ble"disadvantage. I The present invention is based on the observation that the dyestuffs of thespecifiedtype' can also be dyed from an acid bath in a manner satisfying all commercial requirements when the operation is conductedaccording to'a new process to e be outlined below. j By means of this process the hitherto limited scope of application of the dye tuffs of this type is extended in avaluable The new process for thedyeing from an acid bath consists in that'ortho':ortho'edihydroxw monoazodyestuifs, which are suitable per s for dyeing from" a neutral weakly alkaline, but not from an acid bathfa're dyed in the presence of an orthoeorthofedihydroxyn'ionoazo dye'stuff whichis. actually suitable for dyeing rrom'an acidbat., j Q Q Under the term orthoz ortho dihydroxymonoazo dyestuffsare to be understood such monoazo dyestuffs as contain the molecule the atom grbllping a I e BE-l .whi chare "suitableifor: dyeing from fa neutralrt'o weakly alkaline butnotfrom, an acidibath', ;are for example those; whicnalthoughcthey contain no '5 actual nsolubilizing n groups isuch. :as sulfonic acid or carboxyl groups are still sufficiently' soluble forapplicationindyebaths, for example in theform ofltheir alkali compounds, t l l .,eX,-;. .'X- o- .1

a /C -,N=N-C\ (wherein one X indicates hydrogen and the other X an alkali metal) Such'dyestufisare for example the monoazo dyestuffs free from sulfonic cid andcarboxylfgroups but containing a single nitro group of the 'generalformula I011 (1 3 TN;NTT l r wherein R1 and, R2 both indicate an aromatic radical of the benzene series in which the azo group and the hydroxyl group are. in ortho.-.positionto one another; Further OIthOiOIthO'edihydroxymonoazo dyestuffs, which are suitable for dyeing fromla neutral to weakly alkaline but not from 'anacid bath, ar'eithose which are. free from sulfonic acid andcarboxyl groups and contain in the moleculeasingle sulfonic acid amide group (ortho:ortho'-dihydroxymonoazo dyestuffs with more than one sulfonic acid amidegroup areas a rule also suificiently soluble fordyeing from an acidbath). H W

Furthermore there may also be mentioned as dyestuffs of this-'type those orthocortho dihydroxymonoazo dyestuifs'which contain the radical of a dihydroxynaphthalene.

A numberof orthozortho' dihydroxymonoazo dyestuffs, which are suitable for dyeing from -a neutral to weakly alkalinebut 'notfrom an acid bath, are known (-see forexampleGerman PatentNo. 445,888). Further such dyestuffs can be produced by-methods known perse. Those of thelast given formula can-be obtained'for exampleb'y coupling 'a diazo compound of an amine of the general formula a ll-Uzi fl 0H,,

bin-Rf, Q1

l tL'. NH} wherein R1 indicates an aromatic radicalof the benzene series. inwhich therhy'droxyl group and theamino group are in orthozposition tonone another, with hydroxybenzenesy coupling in orthoposition toltl'ie hydroxyl groups startingmaterials being employed which are free from sulfonic acid,

and carboxyl groups. l

The mentioned ortho:ortho-dihydroxyazo dyestufis containing-sulfonic acidamide groups can be produced by coupling ortho-hydroxydiazo compounds (in this case also preferably such of the benzene series) with-compounds coupling in adjacent position to a hydroxyl' group, as for example lrphe ylfi:methrlefi-nrmzobnes 1W1 droxy-na h halen srsta tins m ialsib n emr' p yed -W 011 ar tree from-sulfim aci la ldl ca of ortho ortho dihydroxymonoazo dyestuffs which are suitable for dyeing from a neutral to weakly alkaline but not from an acid baththere are concerned for example: 4- or -nitro 2- amino-l-hydroxybenzene, 5-nitro 4 methyl-2- amino-l-hydroxybenzene; 6-acetylamino-4-nitro- Z-amino-l-hydroxybenzene, 4-acetylamino-6-nitro-2-amino-l-hydroxybenzene;.5 nitro--chloro- 2-amino-1-hydroxybenzene, 6 nitro-4-chloro-2- amino l hydroxybenzene, 4-nitro-6-chloro-2- amino-l-hydroxybenzene, 4 chloro-2-amino-1- hydroxybenzene, -chloro-fi-acetylamino-2-amino-l-hydroxybenzene, Z-amino 1 hydroxybenzenel-sulfonic acid amide; as coupling componentsthere may be employed: hydroxybenzenes substituted in para-position to the hydroxyl group by alkyl or alkoxy groups as for example 4-methyl-l-hydroxybenzene, 4-tertiary amyl-l-hydroxybenzene, 3: i-dimethyl l-hydroxybenzene, 2-acetylamino-ei-methyl-l-hydroxybenzene, 2-acetylamino-4-methoxy-l-hydroxybenzene, 4 isopropyl1-hydroxybenzene, 4-n-butyl-l-hydroxybenzene; furthermore py'razolones'such as l-phenyl- 3-methyl 5 pyrazolone, 1-phenyl-3-methyl-5 pyrazolone-3'sulfonic acid amide, l-phenyl-3- methyl-5-pyrazolonee3i-sulfonic acid anilide and further also polynuclear systems such as 2 :4-.dihydroxyquinoline, 2:3:-, 2:4.--, 2:6-, 217-, l:5-'-dihydroxynaphthalene, 1.-hydroxynaphthalene-3V-, -4- or -5-sulfonic acid amide, 2-hydroxynaphthalene-G-sulfonic acid amide, s Z-hydroxynaphthalene-fi-sulfonic, acid anilida, s

Such dyestuffs are; as arule suitable for, dye.- ing, especially for the dyeing of wool from aneurtralto weakly alkaline bath. Theyare primarily suitable for dyeing by the known single bath chrom ing process, in which, dyeing iscarriedout in the presence ofxanlalka n chromate nd of ammonium sulfate and in; whichv in contradistinction to certain;earlier -literature references-sit is notanacid butenormally a; neutral to weakly l l ne dyeba-th which S;used:-

It: is certain y c tom ry in} hi pr cesso ad s acetic acid in thcl soult ew i ther i ins: n ra tion; the addition -in general only takes place when the ioritynistheldye tuftsla readyfixed on the fiber and the dyeingprocessis ithus practically complete, its effect being to cause to take on the fiber those small residues which are still present in the dyebath.

As ortho:ortho-dihydroxymonoazo dyestuffs suitable per se for dyeing from antacid bath and in the presence of which vdyeingis conducted in accordance with the present .process,. suitably such are employed aswcontain as solubilizing groups a carboxyl group or. a sulfonic: acid group or the atom grouping i1 ortho ortho dihydroxyazo dyestuffs 4 Color Index under Nos, 172'; 202 and 652, and the dyestuffs of the formula OH OH I (IF-CH:

The ratio ofthe quantity of thedyestuff not suitable for dyeing from an acid bath to thequantity. of the dyestufi. which is suitable for dyein froman acid bath can inthe presentprocessovary within widelimits. An, addition of, 30v partspof a dyestufi suitablefor dyeing from an acid bathfi ,parts of a dyestufiwhich is notsuitablefor dyeing from an acid bath alreadyrenders possiblevacommercially satisfactory dyeing and yiel s a; goodjresult, It approximately equal quantities of the two dyestuiis are employedthensfrom an acid bath, dyeings, are obtainedwhich aresfor practical purposes as uniform as those obtained with the dyestufi. which issuitable for, dyeing froman a i athused alona.

p The combined, application of thetwo types of dyestuff according to the present processis inno way limited to .theapplication ofsoneonly of the dyestuffs of each type. With equally good. re,- sults two or more can be employed at the same time of the dyestuffs suitable for dyeing from an acid bath and/or of the dyestufis whichuare not suitable for dyeing froman acid bath;

Ingeneralit is adyantageous to carry outthe dyeing according to the present process in the presence of a weak acid, preferably in the presence of acetic acid and in the absence of mineral acid. As soon as the dyestuifs have for the most part taken on the fiber-,- for the fixation of small quantities of dyestuff still present in the dyebath it is" however possible to I add without disadvan tage andin many: cases with advantage a quantity of sulfuric acid.

7 The preparation of the dyebaths servingfor the execution ofrthe present process suitably takes place using the customary stock solutions which contains the dyestuffs dissolved in the desired mixture ratio 'andliinvconsiderably higher con:- centration than is customary for "the dyebaths themselves. If desired the acid can subsequently be added to such stock solution which are suitably of approximately neutral reaction.

By the mixing of the dyestuffs, advantageously in dry form, valuable dye preparations are obtained. These dye preparations are characterized in that they contain an orthozortho -dihye droxymonoazo dyestufi which per se is suitable for dyeing from a neutral to weakly alkaline but not from an acid bath and an ortho:ortho'- dihydroxymonoazo dyestufi suitable per se for dyeing from an acid bath.

It is in general to be recommended not to admix with these dye preparations substanceshav ing a salting out eifect as for example sodium sulfate or sodium chloride, as. otherwise the good solubility of the preparationsis reduced and the production of concentrated solutions, for example of the above-mentioned stocksolutions may be rendered more difiicult. i

The present process and the preparations of the specified constitution suitable for carrying it out, are primarily suitable for the dyeing of animal fibers, especially for the dyeing of W001 and preferably of loose wool or carded wool. The ortho:ortho'-dihydroxymonoazo dyestuffs which are per se unsuitable for dyeing from an acid bath and which are to be employed in this process, when dyed alone from an acid bath on such fiber material yield quite particularly non-uniform and very often completely useless dyeings. This is easily understandable since these dyestuffs are precipitated by the acid present in the dyebath in coarse form and in this condition cannot penetrate sufiiciently deeply into the material to be dyed; they are retained by the outermost fiber layers which act as a filter. However by working according to the present process, in a surprising manner the dyestuffs remain in solution even in the acid medium or at least in such a fine state of division that the material to be dyed is no longer capable of acting as a filter and becomes uniformly dyed throughout. The new process and the new preparations are accordingly of especial advantage for machine dyeing in which as a rule concentrated dyebaths are used and the material to be dyed is treated in relatively close form in the bath so that the filter efiect tends to be large. Under machine dyeing are to be understood in this case those dyeing methods in which the material to be dyed remains stationary and the dyebath is caused to move, for example by means of a circulating pump.

Among the dye preparations of the constitution set forth above those are of special advantage which contain ortho:ortho-dihydroxymonoazo dyestuffs which are suitableper se for dyeing according to the single bath chroming process but are not suitable for dyeing according to the after-chroming process on account of insufiicient solubility in the acid medium, and at the same time such ortho:ortho'-dihydroxymonoazo dyestuffs as are suitable both for dyeing according to the single bath chroming process and also for dyeing according to the after-chroming process;

With these multiple purpose preparations very valuable fast and level dyeingsare obtained for Example 1 J p A dye preparation is prepared by producing a uniform powder mixture from:

parts of the dyestuff of the formula Wool can be dyed in an advantageous manner with this mixture according to the following dyeing directions. I

100 parts of loose wool are dyed in the following manner with 1.3 parts of the dyestufi mixture obtained according to this example in the dye machine (by this is to be understood a dyeing apparatusin which the material to be dyed is not moved while the dyebath is circulated): H

1.3parts of the mixture are dissolved in about 100 times the quantity of hot water and with this stock solution a dyebath produced which contains in 2500 parts of water at 50 C. in addition to the dyestuff mixture 10 parts of crystalline sodium sulfate and 3 parts of acetic acid of 40 per cent. strength. This dyebath is now run into the apparatus containing 100 parts of loose wool. With example on wool both by the single bath chrom ing process and also by the after-chroming process, the result being to a far reaching extent independent of the nature of the wool to be dyed.

The following examples illustrate the invention, the parts and percentages being by weight unless otherwise stated:

continuous circulation of the dyebath heating to boiling is efiected within half an hour, after 45 minutes boiling 5 parts of 10 per cent. sulfuric acid are added and the whole further treated at the boil for a quarter of an hour. Cooling is then carried out to 70-80 C., 1.3 parts of potassium bichromate are added and chroming efiected for 40 minutes at boiling temperature. Finally the wool is rinsed with cold water and dried. ,It is: dyed a level brown shade.

Instead of employing the mixture produced according to the above directions for the production of the stocksolution, the dyestufis can also be dissolved consecutively in corresponding quantity proportion in about parts of water and the stock solution produced in this way employed according to the same directions, whereby practically the same resultisobtained.

Instead of dyeing with 1.3 parts of the above specified mixture, the loose wool can also be dyed with 1.3 parts of the following mixture in. the same way, a level, reddish brown dyeing then likewise being obtained. i

50 parts "of the dyestufi of the Formula I (see above) 7 14 parts of the dyestuftof tlieiormula HO-sk NV Y ,7

(Sodium salt) a1 CHz-C-CH:

'50 parts of the dyestuff of the Formula I (see Example 1) 36 parts of the'dyestuff of the Formula II (see Example 1) 14 parts of the-dyestuff of the formula (I)H OH HO3S- N=N (Sodium salt) 100. parts;

1.1: parts of. this mixtureare dissolved 111.100.

partsxofihot water. This stock solution is. diluted with waterto. 4000 parts. by volume and parts of crystalline sodium sulfate and 4-. parts of 40 per cent, acetic acid added. 100 parts of loose wool are entered into thedyebath thus obtained at..50. 0., heating isefiected. within half anrhour toboiling'and' dyeing at the boil carried on for minutes. 5 parts of 10 per cent. sulfuric acid are nowadded and boiling continued for a further- 15 minutes. At this point the whole is cooled to -80" 0., 1.3 parts of potassiumbichromate introduced and chroming carried'out at "boiling temperature for 40'minutes.. Finally the wool is rinsed in cold'water and dried. It

is uniformly. dyed in reddish brown shades.

Further, valuable dyeingsare obtained with the mixturesset out in thefollowing table. In'these cases it is possible either; as statedabove, to produce powder mixtures 01' to dissolve the; dyestuffs in corresponding mixture ratio in about parts'of water andto employ for dyeing the stock. solution thus obtained. Column I contains the data relating to the dyestuffs Which'are not suitable for dyeing from an acid bath and column'II the data relating to dyestuffs'which are suitable for dyeing from an acid bath. In column" IIIv is. given the'color shade which is obtained in the dyeing of wool with these mixturesaccording to the dyeing methodsv above set forth. r r

I II III OH OH OH OH I noas- N=N-C 501N112 o N C:

C Ha -C-GHa 1H5 bordeaux. 57 28.5 parts HOaS N=N-O I CH:

14. 5 parts OH (3H OH H? 01N- N=N.

' black grey OQN OaNH: 0,11 36 parts 64 parts OH OH OH OH N=N 0,

navy blue. OzN- I I 1 OH 0111 36 parts 64 parts a OH OH OH OH I c-N i Ho,s N=N-O OPNH c: OQN

CH: A

Cl Or NH bluish bordeaux. Parts 40 parts OH E 0 H033 N=N G\ I V F CH:

1 20 parts OH OH OH OH N=N- H0zS-@-N=N SO NH: Cl OzNH" 30 t 30 t violet brown.

par 5 par s 0H OH C-N- HO|S- N: -C\ I N 40 parts :11 Level dyeings are also obtained wheninone of the mixtures set forth above (Examples 1 and by the dyestufis of the formula on OH Q-N NO NHC c H;

N02 OCHa 1. A process for dyeing woolwhich comprises conducting the dyeing from an acid bath with an ortho ortho -dihydroxymonoazo which per se is soluble in a dyebathhaVing a pH value greater than 6.3 and up to about 8 but which is practically insoluble 'in'a dyebath of which the pH valuelies substantially below 6.3, in the presence of an ortho:ortho'-dihyroxymonoazo dyestuff which per se is soluble in a dyebath having a pH value below 6.3.

2. A process for dyeing wool which comprises conducting dyeing from an acid bath with an ortho ortho -dihydroxymono azo dyestufi which per se is soluble in a dyebath having a pH value greater than 6.3 and up to about 8 but which is practically insoluble in a dyebath of which the pH value lies substantiallybelow 6.3, which dyestuff is free from sulfonic acid and carboxylic acid groups, contains a single nitro group andcorrcsponds to the formula on on iilN=N-i iz wherein R1 and R2 each stand for an aromatic radical of the benzene series in which the azo group and the hydroxyl group are in ortho-position to one another, in the presence of an ortho ortho'-dihydroxymonoazo dyestufi which per se is soluble in a dyebath having a pH value below 3. A process for dyeing wool which comprises conducting dyeing from an acid bath with an ortho ortho -dihydroxymonoazo dyestuif which per se is soluble in a dyebath having a pH value greater than 6.3 and up to about 8 but which is practically insoluble in a dyebath of which the pH value lies substantially below 6.3, which dyestuff is free from sulfonic acid and carboxylic acid groups, contains a single sulfonic acid amide group and corresponds to the formula OH on lt -N=N-l tz wherein R1 stands for an aromatic radical of the benzene series and Rz-OH for the radical of a coupling component, both OH groups being in adjacent position to the azo group, in the presence of an orthozortho-dihydroxymonoazo dyestuif which per se is soluble in a dyebath having a pI-I value below 6.3.

4. A process for dyeing wool which comprises conducting dyeing from an acid bath with an ortho:ortho'-dihydroxymonoazo dyestuif which per se is soluble in a dyebathhaving a pH value greater than 6.3 and up to about 8 but which is practically insoluble in a dyebath of which the pH value lies substantially below 6.3, which dyestuff is free from sulfonic acid and carboxylic dyestuff .2) the dyestuffof the. Formula .I isfreplaced 12 acid groups, contains-a single sulfomc acid amide group and corresponds to the formula wherein R1 stands foran aromatic radical of the benzene series in which the azo group and the hydroxyl group are in ortho-position to one another and R3 stands for a phenyl radical, in the presence of an ortho:ortho-dihydroxymonoazo dyestufl which per se is soluble in a dyebath having a pH value below 6.3.

5. A process for dyeing wool which comprises conducting dyeing from an acid bath with the dyestuif of the formula in the-presence of the dyestuif of the-formula N02 CHs 6. A processfor dyeing wool which comprises conducting dyeing from an acid bath with the dyestuif of the formula in the presence of the dyestuif of the formula NO; CH3

and the dyestuff of the formula 7. A process for dyeing W001 which comprises conducting dyeing from an acid bath with the dyestuif of the formula andthe dyestuif of the formula.

8. A process for dyeing wool which comprises conducting dyeing from an acid bath with the dyestufi of the formula i on; A in the'presence of the dyestuff of the formula 0H 0H i H0zS N=N- 1 o NHO and the dyestuff of the formula 9. A dyestuff preparation containing .an ortho:ortho-dihydroxymonoazo dyestufi which per se is soluble in a dyebath having a pH value greater than 6.3 and up to about 8 but which is practically insoluble in a dyebath of which the pH value lies substantially below 6.3, and an ortho:ortho'-dihydroxymonoazo dyestuff which per se is soluble in a dyebath having a pH value 5 below 6.3.

10. A dyestuif preparation containing an ortho:ortho'-dihydroxymonoazo dyestulf which per se is soluble in a dyebath having a pH value greater than 6.3 and up to about 8 but which is practically insoluble in a dyebath of: which the pH value lies substantially below 6.3, which dyestufif is free from sulfonic acid and carboxylic acid groups, contains a single nitro group and corresponds to the formula 1 1-N=N1 z wherein R1 and R2 each stand for an aromatic radical of the benzene series in which the azo group and the hydroxyl group are in ortho-position to one another, and an ortho:ortho'-dihydroxymonoazo dyestufi which per se is soluble in a dyebath having a pH value below 6.3.

11. A dyestufi preparation containing an "14 ortho:ortho-dihydroxyrnonoazo dyestufi which per se is soluble in a dyebath having a pH value greater than 6.3 and'up to about 8 but which is practically insoluble in a dyebath of which the pH value lies substantially below 6.3, which dyestufl' is free from sulfonic acid and carboxylic acid groups, contains a single sulionic acid amide group and corresponds to the formula wherein R1 stands for an aromatic radical of the benzene series and Rz-OH for the radical of a coupling component, both OH groups being in adjacent position to the azo group, and an ortho ortho-dihydroxymonoazo dyestufl which per se is soluble in a dyebath having apH value below 6.3.

12. A dyestulf preparation containing an 7 ortho:ortho'-dihydroxymonoazo dyestufi? which per se is soluble in a dyebath having a pH value greater than 6.3 and up to about 8 but which is practically insoluble in a dyebath of which the pH value lies substantially below; 6.3, whichdye: stuff is free from sulfonic acid and carboxylic acid groups, contains a single sulfonic acid amide group and corresponds to the formula wherein R1 stands for an aromatic radical of the benzene series in which the azo group'and the hydroxyl group are in ortho-position to one another and R3 stands for a phenyl radicaL. and an orthozortho' dihydroxymonoazo dyestutf which per se is soluble in a dyebath having a pH value below 6.3. I

13. A dyestuif preparation stuff of the formula containing the dye and the dyestuff of the formula I 14. A dyestuif preparation containing the dyestufi of the formula (m OH 15 .theflyestufiofitheformula OZN N=N eNHtCTOQHa I V l lo: $113 and the dyestufi of the formula R l x No; O-CB: V .15. .A;dyestufi preparationcontaining the dyestufi-lofthe formula v r s ozNHz 7 I v CH3 the dyestu'fi of the formula I no3s'-O-N:N-O

' 02H! and the dyestufl of the formula Sol 1 16. A dyestufi preparation containing thedyestuff of-the formula ([1113 the dyestuff of the formula on r on Hoas-O-N=N-8 I 17. A dyebath having a pH :value from 3 to 5 and containing an ortho:ortho'-dihydroxymonoazo dyestuif which per se is soluble in a dyebath having a pH value greater than 6.3 and up to about 8 but which is practically insoluble in a dyebath of :which the pH value lies substantially bath having a pH value greater than 6.3 and up to about 8 but which is practically insoluble in a dyebath of which the pH value lies substantially below 6.3, which dyestuff is free from sulfonic acid and carboxylic acid groups, contains a single nitro group and corresponds to the formula OH OH wherein R1 and R2 each stand for an aromatic radical of the benzene series in which the azo group and the hydroxyl group are in ortho-position to one another, and an orthozortho -dihydroxymonoazo dyestui'f which per se is soluble in a dyebath having a pH value below 6.3.

19. A dyebath having a pH value from 3 to 5 and containing an ortho:ortho-dihydroxymonoazo dyestuff which per se is soluble in a dyebath having a pH value greater than 6.3 and up to about 8 but which is practically insoluble in a dyebath-of which the pH value lies substantially below 6.3, which dyestufi is free from sulfonic acid and carboxylic acid groups, contains a single sulfonic acid amide group and corresponds to the formula wherein R1 stands for an aromatic radical of the benzene series and BzOI-I for the radical of a coupling component, both OH groups being in adjacent position to the azo group, and an ortho:ortho'-dihydroxymonoazo dyestufi which per se is soluble in a dyebath having a pH value below 6.3.

20. A dyebath having a pH value from 3 to 5 and containing an ortho:ortho-dihydroxymonoazo dyestufl? which per se is soluble in a dyebath having a pH value greater than 6.3, which dyestufi is free from sulfonic acid and carboxylic acid groups, contains a single sulfonic acid amide group and corresponds to the formula wherein R1 stands for an aromatic radical of thebenzene series in which the azo group and the hydroxyl group are in ortho-position to one another and R3 stands for a phenyl, radical, and an ortho ortho' dihydroxymonoazo dyestufi which per se is soluble in a 'dyebath having a pH value belo=w.6.3. V

' WILLI WIDMER.

FRITZ SCHUETZ. ALPI-IONSE HECKENDORN.

REFERENCES CITED The following references are of recordlin'the file of this patent:

UNITED STATES PATENTS Number Name Date 2,058,433 Felix r .Oct..27, 1936 2,060,186 Felix Nov. 10, 1936 

1. A PROCESS FOR DYEING WOOL WHICH COMPRISES CONDUCTING THE DYEING FROM AN ACID BATH WITH AN ORTHO''-DIHYDROXMONOAZO DYESTUFF WHICH PER SE IS SOLUBLE IN A DYEBATH HAVING A PH VALUE GREATER THAN 6.3 AND UP TO ABOUT 8 BUT WHICH IS PRACTICALLY INSOLUBLE IN A DYEBATH OF WHICH THE PH VALUE LIES SUBSTANTIALLY BELOW 6.3, IN THE PRESENCE OF AN ORTHO:ORTHO''-DIHYROXYMONOAZO DYESTUFF WHICH PER SE IS SOLUBLE IN A DYEBATH HAVING A PH VALUE BELOW 6.3. 